Bedroom extensions for homes in St Albans
A bedroom extension in St Albans starts with the right design and the right approval route. We take care of both, then build it with our own project management.
- Guide price in St AlbansFrom £27,500 inc VAT
- PlanningUsually a householder application
- Build time14–22 weeks on site
- Postcode districtsAL1, AL2, AL3, AL4
Covering St Albans
Across AL1, AL2, AL3, AL4, we can visit, measure and advise. Neighbouring towns we cover include Harpenden (5 miles), Hatfield (5 miles), Hemel Hempstead (5 miles), Welwyn Garden City (6 miles).
Barnet, in Greater London, is roughly 9 miles from St Albans and also on our list. Across the East of England many houses sit on generous plots, and single-storey and wraparound extensions are a natural fit.
When a bedroom extension makes sense
- Multi-generational households
- Growing families
- Homeowners who want an en-suite master bedroom
New bedrooms on an upper floor need an escape window or a protected route to the outside under the building regulations. We design the window sizes and stair route to meet that from the outset.
Guide prices for St Albans
These guide figures apply our East of England adjustment (×1.06) to national rates. They include VAT at 20% and cover the build itself; design and council fees are listed separately.
Typical rates in St Albans: £1,700 to £3,390 per m² including VAT, depending on specification.
| Size | Essential | Standard | Premium |
|---|---|---|---|
| One bedroom 12 m² | £27,500 – £34,000 | £27,500 – £36,000 | £30,500 – £41,000 |
| Bedroom and en-suite 18 m² | £30,500 – £37,500 | £36,000 – £47,000 | £45,500 – £61,500 |
| Two rooms 30 m² | £50,500 – £62,500 | £60,000 – £78,000 | £76,000 – £102,000 |
For a figure based on your own dimensions, use our guide-price tool.
Planning rules that apply in St Albans
In England a two-storey rear extension is permitted development only if it projects no more than 3 m from the original rear wall, sits at least 7 m from the rear boundary, matches the roof pitch and uses obscure, non-opening side windows upstairs. Most two-storey extensions therefore go through a householder planning application, which costs £548 from 1 April 2026 and normally takes about 8 weeks.
Before any drawing is finalised we check whether the house is listed, in a conservation area or subject to an Article 4 direction.
If the work involves a shared wall, building on the boundary, or digging foundations within 3 m (sometimes 6 m) of a neighbour's building, the Party Wall etc. Act 1996 applies and notice must be served before work starts: two months for work to a party wall, one month for new walls on the boundary and for excavations.
Building regulations approval is separate from planning. In England you can use the council's building control team or a registered building control approver; a full plans application gets the drawings checked before work starts, and the inspector signs the work off with a completion certificate.
Applications are decided by the local planning authority (your district, borough or unitary council).
Our process, step by step
Site visits are free and there is no obligation. Where drawings are needed, the design stage is priced in writing before it starts.
Free site visit
We visit your St Albans home, measure up, talk through what you want and check the planning position.
Design and approvals
We draw the design, agree it with you and handle planning or permitted development checks and building regulations.
Fixed written price
You receive a written, itemised price and programme. Nothing starts until you are happy with it.
Build and sign-off
The build is managed from start to finish, inspected at each stage and signed off on completion.
Your questions about a bedroom extension in St Albans
How long does a bedroom extension take to build in St Albans?
On site, typically 14 to 22 weeks once approvals are in place. Before that, allow 8–14 weeks design and approvals.
Do you cover all of St Albans?
Yes. We cover St Albans and the surrounding parts of Hertfordshire. Site visits are free and there is no obligation.
Do I need building regulations approval in St Albans?
Yes. Almost every extension needs it, whatever the planning route. We prepare the drawings and book the inspections.
Can I add a ground-floor bedroom for a relative?
Yes. A ground-floor bedroom with an accessible shower room is a common request. If it will be lived in as a self-contained home, planning treats it differently, so tell us how it will be used.
Does an en-suite need a window?
No, but it needs mechanical extraction that meets the building regulations. We design the duct route at the drawing stage.
Book a free site visit in St Albans
We will measure up, check the planning position and give you honest guide figures.
- Free, no-obligation site visit
- Planning route checked before you spend on drawings
- Written price once the design is agreed
- Building control sign-off at the end
Prefer to talk? Call 0800 088 6341 or .
Book a free site visit
Tell us a little about the project and we will arrange a time.